Wireless transmitters utilizing phased array antenna panels employ a large number of power amplifiers to amplify radio frequency (RF) signals to transmit directed RF beams. Amplifying RF signals with time-varying amplitude (also referred to as “variable envelope signals”) is not as power efficient as amplifying RF signals with constant amplitude (also referred to as “constant envelope signals”). Moreover, power amplifiers utilized to amplify and transmit constant envelope signals are less non-linear and introduce less distortion as compared to power amplifiers utilized to amplify and transmit variable envelope signals. On the other hand, communicating using RF signals with time-varying amplitude is more spectral efficient than communicating using RF signals with constant amplitude.
In one solution, a variable amplitude signal is decomposed into two constant amplitude signals, and the two constant amplitude signals are amplified using two separate power amplifiers. The two constant amplitude signals are then transmitted over the air by respective antennas. One shortcoming of this solution is that path differences of the two constant amplitude signals will increase the error vector magnitude (EVM). Additionally, particularly in high-frequency applications, phased array antenna panels may transmit RF beams in unintended directions (also referred to as “grating lobes”), interfering with proper reception of intended RF beams. This effect is exacerbated where a phased array antenna panel transmits multiple intended RF beams.
Thus, there is a need in the art to use phased array antenna panels having constant amplitude decomposed RF signals to achieve a transmitter and a wireless communication system that overcome the deficiencies in the art.